Conventionally, a slush molding product of vinyl chloride type resin powder has been used as a skin material for automotive interior parts such as instrument panels and door trim.
The vinyl chloride type material, however, deteriorates in softness during a long time use since the plasticizer contained therein moves toward the surface during a long time use, depending on the use environments. Further, at the time of incineration processing after a used car is disposed, hydrogen chloride gas may be generated depending on the incineration temperature and may cause corrosion of an incinerator in some cases.
To solve these problems, development of a powder slush molding material mainly containing a thermoplastic polyurethane resin powder has been promoted. The powder slush molding method is a method for molding a skin material by filling a die heated to 200 to 300° C. with a powder, rotating the die for depositing the powder to the inner face of the die, discharging the un-deposited powder out of the die, and recovering the powder.
However, the thermoplastic polyurethane resin powder for slush molding causes blocking with the lapse of time when it is left as it is and is deteriorated in the powder flowability. To improve these phenomena, it has been tried to add a maleimide copolymer fine particle powder or a thermoplastic resin powder which is not thermally melted at 160° C. or lower as a powder flowability improver (e.g. reference to Patent Document No. 1 and Patent Document No. 2).    Patent Document No. 1: Japanese Patent Application Laid-Open (JP-A) No. 10-77403    Patent Document No. 2: JP-A No. 2000-17033